An optical semiconductor device such as a photocoupler or a photo relay is generally provided with a light-emitting element such as a light-emitting diode, a light-receiving element such as an optical electromotive diode, for example, and a driving MOSFET mounted on lead frames respectively, wherein the light-emitting element and the light-receiving element are arranged facing to each other and are sealed in a resin mold (for example, refer to Japanese Patent Application 2003-8050).
FIG. 1 shows an example of a photorelay of the double seal structure of a conventional optical semiconductor device. As shown in the drawing, a light-emitting element 103 is mounted on a lead frame 101a, and a light-receiving element 105 and a MOSFET 106 are mounted on a lead frame 101b, wherein they are arranged facing to each other. These elements are primarily sealed by a light-transmitting resin 107 and are secondarily sealed by a light-blocking resin 108. The light-emitting element 103 is bonded to the lead frame (not shown) and the light-receiving element 105 is bonded to MOSFET 106 connected to a lead frame (not shown) by wires 104.
This photo relay is formed as described below. Firstly, as shown in FIG. 2, the light-emitting element 103, the light-receiving element 105, and the MOSFET 106 are respectively mounted on the lead frames 101a and 101b processed to be bent at their end portions. Then, the lead frames 101a and 101b are so arranged that the light-emitting element 103 and the light-receiving element 105 are facing to each other, as shown in FIG. 3.
Next, the light-emitting element 103, the light-receiving element 105 and the MOSFET 106 are primarily sealed by the light-transmitting resin 107 to form a light transfer path, as shown in FIG. 4. Then, these elements primarily sealed are secondarily sealed by the light-blocking resin 108 to block off the light and protect the elements as shown in FIG. 5. Thereafter, the lead frames 101a and 101b are formed to produce the optical semiconductor device shown in FIG. 1.
In recent years, miniaturization of optical semiconductor devices has been strongly required in correspondence to realization of high performance of a semiconductor device and improvement of assembly density. However, since the light-emitting element 103 and the MOSFET 106 are arranged side by side on the lead frame 101b, as mentioned above, miniaturization of the package is difficult for such structure of the optical semiconductor devices.
Further, a method for manufacturing the devices is required to include a step of arranging the lead frames so that the light-emitting element and the light-receiving element are facing to each other, and a step of sealing them with retaining them in the situation described above. Thus it is difficult in the conventional manufacturing steps to shorten the lead time and to cut-down the manufacturing cost by reduction of the number of steps.